In the small but cohesive Mormon community where he grew up, Hans Mattsson was a solid believer and a pillar of the church. He followed his father and grandfather into church leadership and finally became an “area authority” overseeing the Church of Jesus Christ of Latter-day Saints throughout Europe.

When fellow believers in Sweden first began coming to him with information from the Internet that contradicted the church’s history and teachings, he dismissed it as “anti-Mormon propaganda,” the whisperings of Lucifer. He asked his superiors for help in responding to the members’ doubts, and when they seemed to only sidestep the questions, Mr. Mattsson began his own investigation.

But when he discovered credible evidence that the church’s founder, Joseph Smith, was a polygamist and that the Book of Mormon and other scriptures were rife with historical anomalies, Mr. Mattsson said he felt that the foundation on which he had built his life began to crumble.

Around the world and in the United States, where the faith was founded, the Mormon Church is grappling with a wave of doubt and disillusionment among members who encountered information on the Internet that sabotaged what they were taught about their faith, according to interviews with dozens of Mormons and those who study the church.

“I felt like I had an earthquake under my feet,” said Mr. Mattsson, now an emeritus area authority. “Everything I’d been taught, everything I’d been proud to preach about and witness about just crumbled under my feet. It was such a terrible psychological and nearly physical disturbance.”

Mr. Mattsson’s decision to go public with his disaffection, in a church whose top leaders commonly deliberate in private, is a sign that the church faces serious challenges not just from outside but also from skeptics inside.

Greg Prince, a Mormon historian and businessman in Washington who has held local leadership positions in the church, shares Mr. Mattsson’s doubts. “Consider a Catholic cardinal suddenly going to the media and saying about his own church, ‘I don’t buy a lot of this stuff,’ ” Mr. Prince said. “That’s the level we’re talking about here.”

He said of Mr. Mattsson, “He is, as far as I know, the highest-ranking church official who has gone public with deep concerns, who has had a faith crisis and come forward to say he’s going to talk about it because maybe that will help us all to resolve it.”

Every faith has its skeptics and detractors, but the Mormon Church’s history creates special challenges. The church was born in America only 183 years ago, and its founder and prophet, Joseph Smith, and his disciples left behind reams of papers that still exist, documenting their work, exposing their warts and sometimes contradicting one another.

“The Roman Catholic Church has had 2,000 years to work through the hiccups in its history,” said Terryl L. Givens, a professor of English, literature and religion at the University of Richmond and a Mormon believer. “Mormonism is still an adolescent religion.”

Mr. Givens and his wife, Fiona, recently presented what they called “Crucible of Doubt” sessions for questioning Mormons in England, Scotland and Ireland. Hundreds attended each event.

“Sometimes they are just this side of leaving, and sometimes they are simply faithful members who are looking for clarity and understanding to add to their faith,” said Mr. Givens, who hosted a similar discussion in July in Provo, Utah, and has others planned in the United States. The church is not sponsoring the sessions, Mr. Givens said, but local bishops give their permission.

Eric Hawkins, a church spokesman, said that “every church faces this challenge,” adding, “The answer is not to try to silence critics, but to provide as much information and as much support as possible to those who may be affected.” Mr. Hawkins also said the Mormon Church, which counts 14 million members worldwide, added about one million members every three years.

But Mr. Mattsson and others say the disillusionment is infecting the church’s best and brightest. A survey of more than 3,300 Mormon disbelievers, released last year, found that more than half of the men and four in 10 of the women had served in leadership positions in the church.

Many said they had suffered broken relationships with their parents, spouses and children as a result of their disbelief. The study was conducted by John Dehlin, a Ph.D. student in psychology at Utah State University and the founder of “Mormon Stories,” a podcast of interviews with scholars and church members, many critical toward the church.

Some church leaders are well aware of the doubters in their midst. Elder Jeffrey R. Holland, who serves in the church’s Quorum of the Twelve Apostles (the governing body just below the three-member First Presidency), said in April while addressing the church’s semiannual general conference in Salt Lake City: “Please don’t hyperventilate if from time to time issues arise that need to be examined, understood and resolved. They do, and they will.”

Photo

Hans Mattsson and his wife, Birgitta, in New York last month. Mr. Mattsson used to oversee the Mormon Church in Europe.Credit
Sara Krulwich/The New York Times

Mr. Mattsson served as a young missionary in England; his wife, Birgitta, is a convert. They raised their five children in the Mormon Church in Sweden, which dates to the 1850s and has about 9,000 members.

He and his twin brother, Leif, both rose through the ranks of leadership, and in 2000, Hans Mattsson became the first Swede ever to be named an area authority. (He served until 2005, when he had heart surgery.) During the week he worked in technology marketing, and on the weekends he traveled widely throughout Europe, preaching and organizing the believers.

“I was just in a bubble, and we felt so happy,” Mr. Mattsson said.

The first doubts filtered up to him from members who had turned to the Internet to research a Sunday school talk. There are dozens of Web sites other than the Mormons’ own that present critical views of the faith.

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■ Why does the church always portray Joseph Smith translating the Book of Mormon from golden plates, when witnesses described him looking down into a hat at a “peep stone,” a rock that he believed helped him find buried treasure?

■ Why were black men excluded from the priesthood from the mid-1800s until 1978?

■ Why did Smith claim that the Book of Abraham, a core scripture, was a translation of ancient writings from the Hebrew patriarch Abraham, when Egyptologists now identify the papyrus that Smith used in the translation as a common funerary scroll that has nothing to do with Abraham?

■ Is it true that Smith took dozens of wives, some as young as 14 and some already wed to other Mormon leaders, to the great pain of his first wife, Emma?

About that last question, Mr. Mattsson said, “That was kind of shocking.”

Mr. Mattsson said he sought the help of the church’s highest authorities. He said a senior apostle came to Sweden at his request and told a meeting of Mormons that he had a manuscript in his briefcase that, once it was published, would prove all the doubters wrong. But Mr. Mattsson said the promised text never appeared, and when he asked the apostle about it, he was told it was impertinent to ask.

(Mr. Mattsson refused to identify the apostle, but others said it was Elder L. Tom Perry, a member of the Quorum of the Twelve Apostles. Elder Perry, now 91, confirmed through a church spokesman that he did visit a branch in Sweden with skeptical members, but said he recalled satisfying their questions with a letter written by the church’s history department.)

That encounter is what really set off Mr. Mattsson’s doubts. He began reading everything he could. He listened to the “Mormon Stories” podcasts. And he read “Joseph Smith: Rough Stone Rolling,” a biography by Richard Lyman Bushman, a historian at Columbia University and a prominent Mormon.

Mr. Bushman said in a telephone interview: “You would be amazed at the number of Mormons who don’t think Joseph Smith practiced polygamy. It just wasn’t talked about. It was never mentioned in church periodicals. That was policy.”

In the last 10 or 15 years, he said, “the church has come to realize that transparency and candor and historical accuracy are really the only way to go.” The church has released seven volumes of the papers of Joseph Smith and published an essay on one of the most shameful events in church history, the Mountain Meadows massacre, in which church leaders plotted the slaughter of people in a wagon train in 1857.

But the church has not actively disseminated most of these documents, so when members come across them on Web sites or in books, Mr. Bushman said, “it’s just excruciating.”

“Sometimes people are furious because they feel they haven’t been told the truth growing up,” he said. “They feel like they were tricked or betrayed.”

Mr. Mattsson said that when he started sharing what he had learned with other Mormons in Sweden, the stake president (who oversees a cluster of congregations) told him not to talk about it to any members, even his wife and children. He did not obey: “I said to them, why are you afraid for the truth?”

He organized a discussion group in Sweden, and more than 600 participated, he said. In 2010, the church sent two of its top historians, Elder Marlin K. Jensen and Richard E. Turley Jr. to allay the Swedes’ concerns. They had a remarkably frank and sometimes testy exchange, especially about Smith and polygamy.

The Mattssons have tried other churches, but they are still attached to their Mormon faith. A few weeks ago, they moved to Spain for health reasons, they said. They left behind some family members who are unhappy with Mr. Mattsson’s decision to grant interviews to The New York Times and to the “Mormon Stories” podcast.